GE GFK-0804B RTU Message Length, Function Code And Name, Response Message Length Less CRC Code

C

RTU Message Length

To generate the CRC±16 for any message, the message length must be known. The length for all types of messages can be determined from the table below.

Function Code And Name

0

1Read Output Table

2Read Input Table

3ReadRegisters

4ReadAnalogInput

5Force Single Output

6Preset Single Register

7Read ExceptionStatus

8±14 Loopback/Maintenance

16PresetMultipleRegisters

17Report Device Type

18±127

128±255

Query or Broadcast

Message Length Less CRC Code

Not Defined 6 6 6 6 6 6 2

Not Defined 7 + 7th byte 1 2

Not Defined Not Defined

Response Message

Length Less CRC

Code

Not Defined

3 + 3rd byte 1

3 + 3rd byte 1

3 + 3rd byte 1

3 + 3rd byte 1

6

6

3

Not Defined 6 8

Not Defined 3

1The value of this byte is the number of bytes contained in the data being transmitted.

C-8 Micro PLC Programmer's Guide ± April 1994 GFK-0804B